Peristaltic pumps have been used in the past to provide a positive displacement of fluids to achieve pumping of the fluids. In conventional peristaltic pumps, a fluid within a flexible tube fitted within a casing is typically used. In such pumps, one or more rollers or shoes are rotated within the casing and compress the tube; as the roller or shoe compresses the tube in one location, the compression forces the movement of the fluid within the tube. Once the roller passes the location, the absence of fluid within the tube in that location induces the flow of fluid to that location in the tube. In conventional applications, the fluid to be pumped with a peristaltic pump is often sterile or of such a nature that it is desirable to avoid having the fluid contact any of the pump. Peristaltic pumps are useful for a wide variety of applications, including dialysis machines, metering pumps, dosing pumps, heart bypass pump machines, drug dispensing systems, infusion pumps, aquariums, analytical instruments, food and pharmaceutical manufacturing operations, and so forth.
In some applications, it is desirable to have a peristaltic pump which has multiple heads, each having multiple rollers. In such pumps, it is therefore possible to simultaneously pump fluids located within multiple tubes. Such peristaltic pumps are sometimes said to have multiple channels. In addition, cartridges have been used in some conventional peristaltic pumps to make it easier to connect and disconnect tubing from the pump. For example, U.S. Pat. No. 7,214,038, issued on May 8, 2007, to Saxer et al., which is hereby incorporated by reference herein, discloses a removable cartridge which can be connected or disconnected from a peristaltic pump by a user with relative ease. Such a peristaltic pump and cartridges for same are commercially available from Ismatec, S.A., of Glattbrugg, Switzerland. In such conventional peristaltic pumps, it is conventional to have a single rotor which drives a shaft having one or more heads, with each head having a plurality of rollers. However, such multiple heads cannot be rotated independently of one another, such as a different speeds or the like.
Attempts to provide individual control over the pumping action in multiple channel peristaltic pumps have been made in the past. For example, in U.S. Pat. No. 5,098,261, issued on Mar. 24, 1992, to Bertoncini, which is hereby incorporated by reference herein, a peristaltic pump is disclosed that includes elastic tubes that are stretched to varying degrees and, as a result of the Poisson effect from such stretching, reduces the flow path cross-section area in the tubes to varying degrees, in an attempt to allow variable flow speeds in the tubing located in different channels in the pump.
Still another approach to provide independent control of the channels in a multiple channel peristaltic pump is provided in U.S. published patent application No. 2009/0035165, published Feb. 9, 2009, and listing Chang as an inventor, which is hereby incorporated by reference herein. In Chang, one or more roller segments are selectively locked or decoupled from a drive shaft and can be operated with a desired speed and direction. The pump shown in Chang includes two motors: one for selecting the channel or channels to be driven by a lead screw and the second for rotating the roller heads.
Yet another example of a multi-channel peristaltic pump is described in U.S. published patent application No. 2001/0004143, which was published on Jan. 6, 2011, and names Beiriger et al as inventors, and which is incorporated by reference herein. In Beiriger et al., a multi-channel peristaltic pump is described with individually controlled rollers, which are free to rotate on a single shaft, and each of which is coupled to a worm gear. This approach describes control of the individual channels through the use of independent motors. However, this approach requires a fairly large device in order to accommodate the motors required and the gear mechanisms to translate the motor's rotation to the rollers. In this approach, the rollers need to be spaced further apart than may be desired.
Another example of a multi-channel peristaltic pump used in a blood processing system is described in U.S. Pat. No. 6,695,803, issued on Feb. 24, 2004 to Robinson et al., which is incorporated by reference herein. In Robinson et al., a blood processing system including a peristaltic pump is described with three rollers which are coupled to three different motors and which share a single support shaft which is also used to rotate one of the rollers, with the two other rollers having hollow shafts through which the support shaft extends, with each of these two rollers able to rotate independently of the roller attached to the support shaft.
However, none of the conventional pumps provide as much flexibility and ease of operation as may be desirable, such as by providing a multi-channel peristaltic pump such that an operator can selectively control the speed and direction of fluid flow in each of the channels independent of the other channels. Moreover, none of the conventional pumps provide such flexibility and do so with a compact size.